BOSTON - During the late 1990’s, Dr. Jill E. Stein said she became alarmed when she began digging into possible environmental links to health problems among children.

As a physician, she said, she was concerned about an epidemic of developmental, learning and behavioral disabilities in children. Looking at studies on people and animals, she became convinced that certain toxic chemicals found in industry or homes - lead, mercury, dioxins, manganese and nicotine - could contribute to the disabilities.

Stein, who worked as a staff physician at the Simmons College Health Center in Boston and the Harvard Community Health Plan, co-authored a book called “In Harm’s Way: Toxic Threats to Child Development.” She began pushing state government to clean up incinerators and coal plants. She said she helped persuade the state to update public health advisories to protect women and child from mercury contamination.

It was the start of her long career as a social activist and politician.

“I was trying to do more than push pills on people,” she said.

These days, Stein, 60, the Green-Rainbow candidate for governor, is offering some prescriptions for change on the campaign trail.

Stein is the only candidate for governor who opposes casinos. She is the lone candidate who is against standardized tests for students such as the Massachusetts Comprehensive Assessment System, saying they are too rigid and harmful for students.

She is also the only candidate who supports government-paid health care for everyone and the legalization of marijuana. She also stands alone in calling for an end to tax breaks approved 15 years ago for big banks, insurers, defense companies and manufacturers to raise money for education and other programs.

The polls show that Stein is facing an uphill fight to win election on Nov. 2. Stein is running fourth, slightly behind independent Timothy P. Cahill, but far back of Republican Charles D. Baker and Gov. Deval L. Patrick, the Democratic incumbent.

CANDIDATE PROFILES

This is the fourth in a four-part series profiling the candidates for Massachusetts governor in the Nov. 2 election. Here are links to the other profiles

Stein is used to trailing in statewide campaigns. She was an unsuccessful candidate for governor in 2002 and a failed candidate for secretary of state in 2006.

Growing up in a Highland Park, an affluent suburb of Chicago, she said she learned about community activism from her father, a business lawyer, and her mother, a homemaker. The Civil Rights movement was in full swing and she said her parents encouraged her to be involved and aware.

When she entered Harvard College, she said she took part in demonstrations against the Vietnam War. She said she went to classes and workshops started by students as alternatives to traditional studies.

She obtained a bachelor’s degree from in 1973 and a doctorate of medicine from Harvard University Medical School in 1979.

She said it became difficult to care for people in a broken system.

She said the health care system is teetering on the brink of collapse. She said the system is getting killed by a blizzard of paperwork and regulations. During debates, she repeatedly says that Massachusetts General Hospital in Boston employs 275 people to process insurance and other paperwork, while a similar hospital in Canada, which has publicly-managed health insurance, has three employees to do the same work.

“The health care system is about to implode right now,” Stein said. “It’s already happening.”

Because of her training and experience as a medical doctor, Stein enjoys a lot of credibility when talking about health care.

The medical profession runs in her family. Her husband, Dr. Richard Rohrer, is a kidney transplant surgeon at Tufts Medical Center in Boston. The couple have two sons, Ben, 27, a student at Tufts University School of Medicine in Boston, and Noah, 24.

Her brother, Dr. Robert Stein, is a neurologist in Rockport, Maine.

Stein supports a “single payer” system that she said would pay for itself by cutting out the red tape caused by insurance companies. Under such a system, the government would pay for all health care in a system based on the model of Medicare, the federal health insurance program for people 65 and older and for the disabled.

In a position paper, Stein says she is concerned about possible health problems caused by marijuana, but she says the effects appear far less harmful than tobacco or alcohol. She said she backs limited legalization of marijuana partly because the black market is creating violence and taxpayers are financing ineffective law enforcement.

Stein said casinos kill jobs in other businesses such as restaurants. She questions why Massachusetts would want to emulate casino states such as Nevada and Jersey, which are reeling from high unemployment, foreclosures and bankruptcies.

She is pledging to work to rescind tax breaks for corporations to help create 50,000 “green jobs” in energy efficiency, sustainable farming, recycling and building of bike paths, public transportation and other infrastructure.

She said her priority will be to overhaul health care. She said the state is paying about $14 billion a year now for various health care programs and a huge amount of the cost is waste and bureaucracy that can be eliminated. She said small businesses - the engines for growing jobs - are especially being hurt by the high costs of health insurance.

“We are not going to fix anything else until we fix the health care problems,” she said.